Calender air doctor



July 25, 1961 c. E. YOUNGCHILD 2,993,432

CALENDER AIR DOCTOR Filed Jan. 14, 1958 2 Sheets-Sheet 2.

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fi M, 4 *W United States Patent 2,993,432 CALENDER AIR DOCTOR Casper E.Youngchild, Appleton, Wis., assignor to Beloit Iron Works, Beloit, Wis,a corporation of Wisconsin Filed Jan. 14, 1958, Ser. No. 708,881 2Claims. (Cl. 100-93) This invention relates to the portion of a papermachine or paper converting machine known as the calender or calenderstack, and more particularly, to an improved nip pressure control incalenders.

Although the instant invention may have utility in other fieldsincluding the pressing, smoothing, ironing or the like treatment of astrip of flexible material, a particularly preferred use is in the papermachine or paper converting machine calender. The operation of suchcalenders is well known and understood in the art. The purpose of thecalender is to compact the paper to some extent and to give it a finesmooth finish. This effect is obtained on both sides of the paper by theuse of friction and pressure. The calender stack comprises a pluralityof upright or vertically aligned calender rolls. One or more of suchrolls is driven and the drive arrangement is such that there is acertain amount of slip between the rolls at each of the nips definedthereby so that a substantial amount of friction acts on the paper as itpasses through each of the calender nips. A controlled amount ofpressure is also applied.

It is conventional practice in the operation of a calender to raise thetemperature of a particular local circumference of a calender roll inorder to increase the calender loading or pressure at that point. Therise in temperature creates an increase in the diameter of the roll atthat point and, therefore, a much higher loading on the paper webpassing through the nip at that particular point. Friction blocks havebeen used for this purpose occasionally, but such blocks tend todisintegrate and pass pants through the nips in the calender.

Some calender stacks are provided with rolls which are bored for theintroduction of steam. The entire roll is heated in this way and coolingair may be blown on the roll locally in order to reduce the diameter ata particular spot. Any of the aforementioned temperature control devicesare employed to compensate for inequalities or streaks which show up onthe reel as hard ridges in the Winding roll.

The instant invention is based upon a novel solution to the problem hereinvolved. The instant invention resides in the use of a hollow doctorback or beam which carries the doctor blade. This hollow beam isequipped to serve as an air manifold. It is equipped with a plurality ofspaced air or gas outlets extending the full length of the roll adjacentthe doctor blade. Hot or cold air is connected to the manifold and aplurality of valve means mounted in association with each of the spacedgas outlets controls the amount of gas or air flowing through anindividual outlet and thus the amount of heating or cooling effectapplied to the calender roll. The operator may easily observe the winduproll and notice any inequalities which may appear. Compensation iseasily and effectively made for such inequalities by mere adjustment ofthe valve means mounted in the manifold so as to obtain a desiredheating or cooling effect in a particular localized area of the calenderroll. For example, if a hard ridge starts to appear on the windup rollat a given location, then the operator adjusts the valves in themanifold along the portion of the calender nip aligned with thisimperfection, so as to heat up a portion of a calender roll in thisarea, thereby to increase the nip pressure.

The doctor is, of course, mounted in close running relation to acalender roll at the ofi-running side of the calender nip; and thiskeeps the calender roll perfectly clean at this region of theoff-running side of the nip. The longitudinally spaced gas outlets inthe manifold mounting the doctor blade are aimed at the calender rollalong a line at the off-running side of the doctor blade, whereatuniform cleanness of the calender roll surface is obtained for bestcontrol in the heating or cooling of the calender roll by theapplication of the gas or air.

It is therefore an important object of the instant invention to providean improved calender, and more particularly, an improved calenderwherein improved means are provided for controlling the loading alongthe full length of calender nips therein.

Another object of the instant invention is to provide an improvedcalender comprising a calender roll, a doctor mounted in close runningrelation to said roll, means mounting said doctor and providing spacedgas outlets extending the length of said doctor aimed at said roll foreffecting localized temperature control along the length of the roll,and gas flow control means for each of said outlets.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached hereto.

On the drawings:

FIGURE 1 is essentially a diagrammatic view showing a calender stackembodying the instant invention in elevation;

FIGURE 2 is a fragmentary top plan view taken substantially along theline l III of FIGURE 1 showing the doctor back;

FIGURE 3 is an elevational view of the doctor back of FIGURE 2 takensubstantially along the line III--III; and

FIGURE 4 is a cross-sectional view of the doctor back of FIGURE 2 takensubstantially along the line IVIV, with the valve means shown in detail(the valve means having been omitted from FIGURES 2 and 3 for purposesof simplification).

As shown on the drawings:

As shown in FIGURE 1, a calender stack indicated generally by thereference numeral 10 comprises a bottom roll 11 and a plurality ofsuperimposed calender rolls 12 through 17 defining a plurality ofsuperimposed nips N1 through N-6. The web W passes over the top roll 17through the first nip N-l around the second roll 16 through the secondnip N-2, etc., until the web finally passes through the bottom nip N6and out to the windup (not shown).

As indicated in FIGURE 1, the rolls 12, 13, 14 and 15 are each furnishedwith a doctor 18, 19, 20 and 21, respectively, which is mounted in closerunning relation to the particular roll with which it is associated. Aswill be noted, the doctor 21 is associated with the roll 15 and it ismounted in close running relation thereto at the offrunning side of thenip N-3. The doctor 21 is mounted on a doctor back, indicated generallyat 22. Although the details of the doctor back 22 will be discussed inconnection with FIGURES 2 through 4, it will be noted that the doctorback 22 is a hollow beam that is connected through a line 23 to a sourceof gas, in this case cold air CA. The cold air passes from the source CAthrough the line 23 and into the hollow doctor back 22. From there it isforced through outlets 24 against the surface of the roll 15 at theoff-running side of the doctor 21. Optionally, the interior of the roll15 may be heated, for example, by steam through a line 25 from a sourceS. In this way the chilling effect of the cold air CA coming throughselected outlets or nozzles 24 is very pronounced on the roll 15 andthere is a substantial temperature differential between the heatedportions of the roll 15 and the chilled or cooled portions exposeddirectly to a blast of cold air through a nozzle 24. Actually, thechilling effeet of cold air alone (without the use of steam in theinterior of the roll 15) will also produce a desirable temperaturecontrol effect. This is shown in connection with the doctor back 26which mounts the doctor 19 in association with the roll 13. Cold airflowing through nozzles or outlets 27 in the doctor back 26 will resultin the desired local temperature control in the roll 13so as to obtainlocalized control of the diameter of the roll 13.

If it is desired to eliminate a localized high spot" or portion ofexcessive thickness in the web W, the cold air coming from the nozzle 24is reduced by valve means 28 at the particular area of this high spotand the tem perature of the peripheral port-ion of the roll 15 in thisregion increases. Thisresults in an increase in the diameter of the roll15 at this region and much greater loading at the nips N-2 or N-3 orboth. Additional increase in the loading of the web at the nips N-4 orN-5 or both may also be obtained by reducing the cold air flow throughselected outlets 27 (using selected valve means 29).

Referring now to FIGURES 2, 3 and 4, it will be seen that the doctorback 22 of FIGURES 2 and 3 is provided with a top inlet 30 (which isconnected to the cold air inlet line 23) and the doctor back 22 isprovided with a plurality of air outlets 24a, 24b, 24c, 240., etc. Theseoutlets 24a, 24b, etc. are spaced longitudinally of the roll so thateach may serve a longitudinally spaced peripheral portion of thesurface. A reduction of the cold air fiow at the outlet24a while thecold air flow is maintained at the outlet 2412 results in a slightincrease in the diameter of the roll just opposite the outlet 24a, sothat greater loading at the press nip is obtained in this region.

FIGURE 4 shows the details of the valve means employed in control of aspecific gas outlet, in this case the outlet 24d. As will be seen fromFIGURE 4, the doctor back 22 has a generally rectangular cross-sectionformed by welding to angle irons 22a and 22!; together at welds x (whichare airtight welds). An end piece such as the end piece 220 of FIGURE 2is, of course, provided at opposite ends of the doctor, back 22 toprovide a closed hollow chamber C. Incoming gas or air is fed into thechamber C through the inlet described in connection with FIGURES 2 and3. Each outlet 24 is defined by a short section of pipe 24d whichthreadedly engages the doctor back at a suitable aperture y in one sideof the angle iron 22a. Opposite the individual aperture y there is asmaller aperture y which mounts a threaded tube 31. The threaded tube 31carries spaced O-rings 32, 32 which function to mount a valve shaft 33and seal the same to prevent loss of air under pressure through the tube31. The valve shaft has a manually graspable handle 34 outside thedoctor back 22 for effecting limited axial movement of the shaft 33. Theinner extremity of the shaft 33 carries a valve closing element 35 isthe form of an oversize rubber washer 35a clamped between the two brasswashers 35b, 35b by a screw 35c threadedly engaging the end of the shaft33.

The doctor blade 21 (shown only fragmentarily) is secured to the doctorback 22 by suitable nut and bolt assemblies 36 as indicated. The gaspasses through. the opening y and the pipe section 24d against the roll15 (shown only fragmentarily) along a portion 15a at the off-runningside of the nip N-3 and at the ofif-running side of the doctor 21. Theamount or" air passing through each individual opening 1 is controlledby axial movement of the valve shaft 33.

It will also be appreciated that hot air can be employed instead of thecold air previously described in connection with the instant device. Forexample, as shown in 4 V FIGURE 1, a source of hot air HA may beprovided and lines 37 and 38, respectively, feed the hot air to thebacks 39 and 49 which mount the doctor blades 20 and 18. The structureof the doctor backs 39 and 40 is the same as that shown in connectionwith FIGURES 2 through 4 and the only difference in function is that hotair rather than cold air is' employed. In such circumstances, additionalloading at a region in the press nip is accomplished by opening thevalve means 41, for example, in the doctor back 40 to permit greaterheating of the desired portion of the roll 12.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

I claim as my invention:

1. In a calender, which comprises a plurality of super- 9 imposed rollsdefining a plurality of nips, a doctor mounted in close running relationto each of said rolls at the oii-running side of the nip and extendingalong the length of the roll, a hollow doctor beam mounting each of saiddoctors, said doctor beam being provided with at least one air inlet anda plurality of air outlets spaced therealong and directing a pluralityof air streams at the roll at the off-running side of the doctor and theoff-running side of the nip for effecting localized temperature controlalong the length of the roll, and valve means controlling each of theair outlets, the improvement in said valve means comprising ahorizontally slidable shaft member mounted by the doctor beam, an airstream-directing pipe member in each outlet generally transverse to theroll opposite thereto, and an outlet closing member at one end of theshaft movable toward and away from each outlet to control the amount ofair released from said doctor beam and through each outlet pipe towardthe roll.

2. A calender, which comprises a plurality of superimposed rollsdefining a plurality of nips, a doctor mounted in close running relationto each of said rolls at the off-running side of the nip and extendingalong the length of the roll, a hollow doctor beam mounting each of saiddoctors, said doctor beam being provided with at least one air inlet anda plurality of air outlets spaced therealong and directing a pluralityof air streams at the roll. at the off-running side of the doctor andthe elf-running side of the nip for effecting localized temperaturecontrol along the length of the roll, and valve means controlling eachof the air outlets, the improvement in said valve means comprising anair stream directing pipe member in each outlet generally transverse tothe roll opposite thereto, directing air to a selected roll area at theregion of contact with the doctor, the pipe member being alignedgenerally parallel with the doctor blade, a movable shaft member, and anoutlet closing member mounted on the shaft member and movable toward andaway from closed position in the outlet to control the amount of airreleased from said doctor beam and through each outlet pipe membertoward the roll.

References Cited in the file of this patent UNITED STATES PATENTS485,534 Dillon Nov. 1, 1892 600,518 Dillon Mar. 15, 1898 680,135 Drew eta1. Aug. 6, 1901 1,326,615 Pope Dec. 30, 1919 1,714,261 Egan et al. May21, 1929 1,982,571 Clark Nov. 27, 1934 2,130,241 MacLaurin Sept. 13,1938 2,184,908 Chan Dec. 26, 1939 2,190,941 Gardner Feb. 20, 1940

